|AESC uses a Mn spinel cathode material. Click to enlarge.|
Nissan Motor, NEC Corporation, and NEC TOKIN Corporation formed the joint venture Automotive Energy Supply Corporation (AESC) in 2007 to develop and market lithium-ion batteries for hybrids, plug-in hybrids and electric vehicles.
With work on all three types of electrified platforms currently underway at Nissan and alliance partner Renault, AESC outlined its current and next-generation cell technology at the Advanced Automotive Battery Conference (AABC) this week in Tampa, FL.
AESC is currently producing laminated lithium-ion cells using a manganese spinel cathode material (LiMn2O4). The laminated structure, said Nobuaki Yoshioka, Senior Executive Vice President of AESC, enables the cells to have low electrical resistance. The large surface area supports high heat radiation, suited for large current charge and discharge.
The crystalline structure of the spinel provides stability and does not collapse in overcharging. The cells offer a high power density of more than 2,000 W/kg.
We have developed cells for HEV so far, but we are now developing a new concept for electric vehicles. EVs are a source of uncertainty [for drivers] for fear of running out of electricity and not being able to refill the tank. We will present that our EVs with the charging function of just a few minutes will provide the driver with an extremely efficient means of resolving the uncertainty.—Nobuaki Yoshioka
|Characteristics of the L3-10 and L3-3 Cells|
|Size (L x W x H)||mm||251 x 144.2 x 9.2||251 x 144.2 x 9.2|
|Power density (2.5V) (25°C 10s @SOC50%)||W/kg||2,060||2,250|
|Power density (1.8V)
(-30°C 2s @SOC50%)
|Performance||High energy||High power|
AESC has its EV batteries under test in the Subaru R1e vehicles being tested in Japan by TEPCO; a quick charge (80% capacity of the 9.2 kWh pack in 15 minutes) is part of the vehicle specification.
AESC’s current EV battery is the L3-10, a 13 Ah, 3.6V laminated cell that uses the same footprint of the L3-3 cell. The material used in the L3-10 is the same as used for HEVs, but AESC thickened the electrode and increased the number of laminate layers to increase the capacity to 13 Ah.
The L3-10 has 3.5 times the capacity of the L3-3.
|Power characteristics of the L3-10 at 25°C. Click to enlarge.|
The discharge rate characteristics of the cell are good because of its low resistance derived from the cell structure; the L3-10 shows high discharge power at a wide SOC range.
With the appropriate quick charge infrastructure, the L3-10 can be recharged to 90% SOC in 15 minutes, with a cell temperature increase of a maximum 8° C. The cell can reach 60% of capacity in 5 minutes.
Based on AESC’s testing, the cells will retain more than 80% capacity after 7 years, including 70,000 km (43,496 miles).
For the next-generation of EV cells, AESC is working on a new cathode material of a nickel-mixed Mn spinel and a graphite carbon anode. The cell will feature an enlarged footprint, but will be thinner to increase heat discharge, and have a capacity of 30 Ah.
With a capacity in excess of 30 Ah, we can cut the number of cells [compared to applications of the L3-10] in half.——Nobuaki Yoshioka
|Fuel economy and vehicle speed by driving distance of a prototype Nissan PHEV. (Fuel economy in mpg, speed in kph.) Click to enlarge.|
Also at the AABC event, Takeshi Miyamoto, Engineering Director, Electronics & Power Electronics Engineering Division, Nissan, said that the internal hybrid drive currently under development at Nissan for deployment in 2010 is a parallel hybrid system.
Nissan has also been testing a 40 km all-electric range plug-in hybrid (PHEV) with the laminated Li-ion cells, with significant demonstrated fuel economy improvements during the charge depleting mode, and fuel economy better than a conventional hybrid vehicle during charge sustaining mode. (See diagram at right.)